The present invention relates to a synchronous control apparatus used for switching function modes of an electronic apparatus with a multi-circuit system driven by different power systems.
A small electronic computer with a time counting function (referred to as a calculator with clock) using a single display for both the functions, for example, has been practically used. Continuous drive of the display device consuming relatively large power is undesirable from a viewpoint of power saving. A countermeasure taken for this is that power is constantly supplied to the time counting block while power is supplied to the operation block only when the operation function is performed or the time counted value is displayed.
This kind of calculator has various functional modes; operation mode or stop mode, set mode for setting time, etc. When the functional mode is switched from one to another, it is desirable that the contents thus far stored or displayed is cleared to be set at the initial value. For example, the functional mode is set at the set mode to set desired time and then it is switched to the operation mode. In this case, under a condition that the computer is not set at the initial condition, if the function key is erroneously actuated, the calculator calculates the contents displayed on the basis of the instruction produced by the key actuation. Failing to take notice of this error, an operator enters new data into the calculator and operates the corresponding function key. In such an operation, the calculator operates on the entered data as the operand, even though he entered it as an operand to be on operated. The result of the calculation is erroneous. It is for this reason that the operator must set the calculator at the initial condition by the corresponding key actuation before its operation, each time that the operator switches the functional mode. This is troublesome in calculator operation.
Therefore, it is desirable to automatically set the respective circuits of the operation block at the initial condition when the mode is switched. By convention, the initial value setting circuit is comprised of a CR circuit including a resistor and a capacitor, and a wave-shaping circuit. In mode switching, the constantly operating time counting block is asynchronous with the operating circuit initial-set through such an initial value setting circuit, since the time constant dependent on the CR is asynchronous with the timing of the internal operation thereof. It is impossible, therefore, to perform a correct transfer of data between the two circuit block.
Accordingly, an object of the present invention is to provide a synchronous control apparatus in a multi-circuit system in which an output signal of a mode switch for setting various modes is transmitted as an initializing signal to a second circuit system through a control circuit of a first circuit system which is constantly operating and thereby the output signal becomes the one synchronizing with the first circuit system whereby, when the mode switch is switched for mode change, the second circuit system may be initialized in synchronism with the first circuit system.